Is this on GTA IV? If you're using native mode on GTA IV, then the server won't be aware of any game elements (including player peds).
You'll need to send the position to the client in a network event to make the client set the position itself, or put the command in a client-side script and process it all there without the server being involved.
You'll need to send the position to the client in a network event to make the client set the position itself, or put the command in a client-side script and process it all there without the server being involved.